The inventive concepts relate to methods of operating a semiconductor memory device and, more particularly, to methods of operating a semiconductor memory device which includes a variable resistance memory element.
Semiconductor memory devices may be classified as either volatile memory devices or nonvolatile memory devices. Volatile memory devices are generally characterized by the loss of stored data when a power supply is interrupted. Examples of volatile memory devices include a dynamic random access memory (DRAM) devices and a static random access memory (SRAM) devices. Nonvolatile memory devices are generally characterized by the retention of stored data even when a power supply is interrupted. Examples of nonvolatile memory devices include programmable read only memory (PROM) devices, erasable PROM (EPROM) devices, electrically EPROM (EEPROM) devices, and flash memory devices.
Other examples of nonvolatile semiconductor memory devices include ferroelectric random access memory (FRAM) devices, magnetic random access memory (MRAM) devices, phase change random access memory (PRAM) devices, and resistive random access memory (RRAM) devices. The devices, which may be referred to as types of variable resistance memory device, are characterized by memory cells having programmable resistance values or states according to a supplied current or a supplied voltage. The programmed resistance values of these memory devices can be maintained even when a power supply is interrupted.